library(tidyverse)
library(wbstats)
library(plotly)

1 Gross Domestic Product (GDP)

We can initially approach the concept of GDP by explaining the terms “Product”, “Domestic” and “Gross” separately (Lequiller and Blades 2014, Chapter 1):

1.1 Data about GDP using Colombia as an example

Initially the units in which GDP is measure is in monetary units of a specific currency, \(c\). Therefore \(GDP_{s}^{c}(t)\) means the \(GDP\) of territory \(s\) in a given period \(t\). To make the discussion less abstract we present a plot of \(GDP\) for Colombia, \(s = COL\), expressed in Colombian pesos, \(c = COP\), for the years 1960 to 2019, \(t = 1960, \ldots, 2019\):

# Clean data
gdp_colombia <- wbstats::wb(country   = "COL",
                             indicator = "NY.GDP.MKTP.CN",
                             startdate = 1960,
                             enddate   = 2019) %>%
    tibble::as_tibble() %>%
    dplyr::select(date, value) %>%
    dplyr::mutate(date       = as.double(date),
                  label_text = stringr::str_glue('Year: {date}
                                                  GDP: {value %>% scales::dollar()}'))

# Plot

static_plot <- gdp_colombia %>%
    # Data
    ggplot2::ggplot(aes(x = date, y =value)) +
    # Geoms
    ggplot2::geom_point(aes(text = label_text),
                        shape = 21,
                        color = "black",
                        fill  = "red") +
    ggplot2::geom_line(linetype = "dashed") +
    # Scales
    scale_x_continuous(breaks = c(1960:2019)) +
    scale_y_continuous(breaks = seq(from = 0, to = 1.10e15, by = 1e14),
                       labels = scales::number_format(scale = 1/1e12, suffix = "B")) +
    labs(x = "Year",
         y = "GDP in current local currency [B = Billion in long scale (10^12)]",
         title = "GDP of Colombia: 1960-2019") +
    # Themes
    theme(panel.border      = element_rect(fill = NA, color = "black"),
          plot.background   = element_rect(fill = "#f3fcfc"),
          panel.background  = element_rect(fill = "#f3f7fc"),
          legend.background = element_rect(fill = "#f3fcfc"),
          plot.title        = element_text(face = "bold"),
          axis.text.x=element_text(angle = -90, vjust = 0.5),
          axis.title        = element_text(face = "bold"),
          legend.title      = element_text(face = "bold"),
          axis.text         = element_text(face = "bold"))

    # Interactivity
    static_plot %>%
      plotly::ggplotly(tooltip = "text")

1.2 A simple economy to explain the measurement of production (Blanchard 2017)

  • In a certain geographical territory \(s\) and in a given period \(t\) there exist \(2\) profit-making enterprises:

    • Steel enterprise

    • Car enterprise

      • The Steel enterprise sells to the Car enterprise steel. Then the Car enterprise uses steel to produce cars an sell them to households located inside or outside the geographical territory \(s\)

      • In that sense the economy uses steel, machinery and labor, known as inputs of production in the field of economics , to produce a final good represented by cars where the production is divided between the owners of the \(2\) enterprises who perceive an income represented by profits and the workers who perceive an income represented by wages.

  • In this simple economy we do not have non-profit institutions and a government that imposes taxes to offer services and goods like public education in \(t\) because the only goods produced are steel and cars.

  • We also assume that production doesn’t accumulate in \(t\). Therefore steel is used entirely to produce cars and all the cars are consumed by households located inside or outside the geographical territory \(s\). Thus, the profit-making enterprises don’t accumulate inventories and distribute all the profits to the owners of the \(2\) enterprises in \(t\).

  • Finally we assume that households inside the geographical territory \(s\) only consume cars produced inside the geographical territory \(s\) and not cars produced outside the geographical territory \(s\) in \(t\). Also, the \(2\) profit-making enterprises don’t buy machines produce outside the geographical territory \(s\) to produce steel or cars in \(t\).

  • We can have a more realistic economy that have:

    • Profit-making enterprises that acummulate inventories or don’t distribute all the profits to the owners

    • Profit-making enterprises that not only produce but pollute the air or the environment

    • Non-profit institutions that by law are requiere not to distribute profits

    • Households located inside or outside the geographical territory \(s\) that save part of their income and don’t consume everything or that engage in illegal activities like robberies

    • Households inside the geographical territory \(s\) that have children and require and education system

    • Households inside the geographical territory \(s\) that consume goods and services produced outside the geographical territory \(s\)

    • A government that imposes taxes to offer services like justice and goods like public education and deliver subsidies

And many other aspects not included in this short list but the idea is to explain in a simple way the measurement of GDP.

  • The above simple economy in a certain geographical territory \(s\) and in a given period \(t\) can be represented in the following way using specific values to be less abstract and expressing every item in specific currency, \(c\), like Colombia pesos (COP):

    • Steel enterprise

      • Steel sales to Car enterprise: \(100 \text{ COP}\)

      • Expenses:

        • Wages: \(80 \text{ COP}\)
      • Profits: \(20 \text{ COP}\)

    • Car enterprise

      • Revenue from sales of cars: \(200 \text{ COP}\)

      • Expenses:

        • Wages: \(70\) COP

        • Steel purchases to Steel enterprise: \(100\) COP

      • Profits: \(30\) COP

1.2.1 Measuring production and the double counting problem

  • If you add in monetary terms the production of both companies you get a total of: Production Steel enterprise \(+\) Production Car enterprise \(=\) Steel sales to Car enterprise \(+\) Revenue from sales of cars \(= 100 \text{ COP} + 200 \text{ COP} = 300 \text{ COP}\)

  • If the production of the Steel enterprise and the Car enterprise is added, the value of steel is being added two times.

  • It is necessary to eliminate at some stage of the production process the value of steel in our example

1.2.2 Three equivalent ways to measure production and avoid the double counting problem

1.2.2.1 GDP as the sum of value added

  • GDP is the sum of value added in a certain geographical territory \(s\) during a given period \(t\) expressed in a local currency \(c\).

  • In the field of economics the value added is the value that is added at each stage of production. It is defined as the difference between the Production in expressed in a Monetary Terms (PMT) and the Consumption of Intermediate Goods (CIG).

    • The PMT is simply the production expressed using a local currency \(c\)

    • The CIG is the monetary value expressed using a local currency \(c\) of inputs that are completely transformed and depleted in the production process and that are used to produce other products.

      • Example of inputs that are not part of the CIG:

        • Wages paid by a profit-making enterprise to its workers: labor can be used for several periods and although its value is affected in the periods close to the age of retirement of individuals, is not fully consumed in the production process.

        • Assets that belong to a profit-making enterprise and depreciation (consumption of fixed capital): assets are durable goods that can be used for several periods and although their value is affected by physical deterioration, foreseeable wear and accidental damage it is important to remember that depreciation (consumption of fixed capital) is included and not deducted in the measurement of GDP.

  • Measuring GDP as the sum of value added using our simple economy:

    • Steel enterprise

      • PMT: \(100 \text{ COP}\)

      • CIG: \(0 \text{ COP}\) (Wages are not part of CIG)

      • Value added: \(100 \text{ COP} - 0 \text{ COP } = 100 \text{ COP}\)

    • Car enterprise

      • PMT: \(200 \text{ COP}\)

      • CIG: \(100 \text{ COP}\) (Wages are not part of CIG)

      • Value added: \(200 \text{ COP} - 100 \text{ COP } = 100 \text{ COP}\)

    • GDP

      • Total Value Added = Value added Steel enterprise \(+\) Value added Car enterprise \(= 100 \text{ COP} + 100 \text{ COP} = 200 \text{ COP} =\) GDP

1.2.2.2 GDP as the sum of incomes

  • GDP is the sum of the incomes perceived by individuals in a certain geographical territory \(s\) during a given period \(t\) expressed in a local currency \(c\).

  • In that sense the GDP can me measure as the sum of the different incomes that individuals perceive like profits and wages

  • Measuring GDP as the sum of incomes using our simple economy:

    • Steel enterprise

      • Workers income: \(80 \text{ COP}\)

      • Owners income: \(20 \text{ COP}\)

    • Car enterprise

      • Workers income: \(70 \text{ COP}\)

      • Owners income: \(30 \text{ COP}\)

    • GDP

      • Total Income = Total workers income \(+\) Total owners income \(= (80 \text{ COP} + 20 \text{ COP}) + (20 \text{ COP} + 30 \text{ COP}) = 200 \text{ COP} =\) GDP

Bibliography

Blanchard, Olivier. 2017. Macroeconomics. 7th ed. Boston: Pearson.

Lequiller, François, and Derek Blades. 2014. Understanding National Accounts: Second Edition. OECD. https://doi.org/10.1787/9789264214637-en.